Cécile Najoux - La ponctuation: A course to learn more about punctuation. How to ponctuate texts, using commas, semicolons, question-marks; what are the other typographic signs used in French, what should be put in italic in a text.
Grammaire interactive Reverso: When to write an exclamation point in French. Provides theoretical information, examples and interesting extra information.
Orthogram.com: French typographical rules. Short explanations are provided on a variety of topics such as abbreviations, capitalizations, writing numbers, ponctuation, and accentuation.